Pavement and process of making



Feb. 23', 192e. T 1; s73,923

H. E. FLETCHER 4- PAVEMENT AND PROCESS 0F, MAKING v' Ax-*iled'rvfawh 28,1923 lNvENTOR ATTORNEY Patented Feb. 23, 192e.

PATENT OFFICE.

HERBERT E. FLETCHER, 0F WESTFORD, MASSACHUSETTS.

PAVEMENT AND PROCESS OF MAKING.

Application filed March 28, 1923.

To all whom t may concern:

Be it known that I, HERBERT E. FLETCHER, a citizen of the United States,residing at llestford, in the county of Middlesex and State ofMassachusetts, have invented certain new and useful Improvements inPavements and Processes of Making, of which the following is aspecification.

This invention relates to roads and the process of building them. y

-In the art of building what are considered permanent roads, it isnecessary to so build that water shall not get in joints, cracks,` orother places in the `road proper' where it can freeze-and thus causebreakage, and so far as possible to keep it out from' underneath wherefreezing and thawing would have a tendency to heave and break the road.

Roads of this character as now constructed include a subbase, generallyvof a natural soil, eitherv excavated to the desired depth and shape, orfilled, and the load carrying top.

`It has been found highly desirable that the top should be continuous tokeep out the water as above described, and that this top `or pavementshould have sufficient beam ,strength to span any soft spots in thesubgrade which have arisen from any cause.

@ne great difficulty encountered has been `the uneven expansion andcontraction on account of heat and cold which goes on 1f the roadbed isreinforced with metal ties, and which also goes on in most structureswhich are not monolithic. Y

I am aware that roads have been built with a base. of concrete or othersimilar monolithic material, and that on this has been placed a cushionof sand or cement, and that upon such cushion or upon the concreteitself, a surface layer of granite blocks, bricks, `or other materialhas been placed.

In roads so constructed, however, the different layers expand orcontract to different degrees and after a time cease to be boundtogether but allow a certain amount of slippage.

In such a case, if there are two layers each four inches thick, thecombined strength is very much less than one monolithic. structure eightinches thick.

It is thepurpose of my invention to provide an homogeneous structurewith a very durable topV wearing surface and one in which the expansionand contraction will be reduced to a minimum, and Ywhat there is will dolittle, if any, harm.

Serial No. 628,382.

Another purpose of my invention is to reduce the cost of such structuresby constructing such a monolithic roadbed of such beam strength andconsistency that less material can be used while still obtaining thedesired strength.

Another object of my invention is to utilize the irregular blocks whichare now waste in stone quarries, particularly, granite quarries, andblocks of various depths.

Suitable blocks for my pavement can be manufactured cheaply from what isnow thrown away as useless except for crushing.

My invention further consists in an improved method of bonding stoneblocks, which form the top part and which are of uneven depth, with theconcrete bottom to provide a monolithic slab or a pavement of therequired strength. This is accomplished by alternating .deep and shallowstone blocks either alternate. stone blocks in each course or inalternate courses or by any arrangement by which adjoining blocks varyin depth sutliciently to effectually bond the stone blocks with theconcrete. By this method, stone blocks of either regular or irregularshape, but of various depths can be used. The results obtained are areduction ot` labor and waste in the manufacture of stone blocks to beused in accordance with this method, and the increased strength of thepavement, one of the large items in the cost of stone blocks to be laidby usual methods being the expenditure of labor and waste of materialnecessary to manufacture stone blocks of uniform depth.

My invention further consists in animproved method of thoroughly unitingthe several parts of the structure into a solid slab pavement by thesequence of operations as hereinafter described so that all parts of mypavement are bonded into a monolithic structure which will not beinjured by ex pansion and contraction from heat and cold.

In the drawings,

Figure l is a cross section of a pavement of my construction and thesurrounding earth.

Fig. 2 is a cross section of diagrammatic form and in part perspectiveshowing some of the modifications which I may use.

F ig. 3 is a plan view of such a pavement as shown in Fig. l.

In the drawings, A represents the natural earth which should beexcavated to form a subg-rade or foundation, the lines of which thefinished surface of the street.

On this subgrade or foundation, I spreadl a mixture B made of brokenstone, gravel or other aggregate, preferably of relatively small sizesuch as might pass through a one inch ring, mixed dry with Portlandcement and sand. A. good mixture is one part'Portland cement, threeparts'sand and six parts broken stone by volume.

The aggregate may be damp when used, but should be free from excesswater. l

The mixture should be thoroughly blended in a mechanical mixer,preferably of the batch type, until it is of uniform color andcomposition. No water is to 'be added before or during the mixing. i

After mixingit is spread on the subgrade to the desired depth and keptdry until the stones or pavingblocks have been properly set and rammedinto place. rlhis mixture B should be covered` with the surfacingblocks-very soon after it is laid before there is any chance for it toharden on account of Vmoisture from the earth or afir. i

For mypreferred type of pavement shown in Fig. 2, I use paving blocks Hand K of substantially box shape and rectangular top faces, but ofvarying depths, the blocks H being deeper than the blocks K.

These are, preferably, laid in courses, suchk Y blocks are packed to afull compact bed in the mixture, which is then a dry cushion. Blocksshould not be laid to any great extent in advance of the rammiiig.

After being laid, they are rammed to make a smooth or relatively smoothsurface, and any which project unduly or are far below the generalsurface are removed and replaced by others. v

These blocks must be so bedded that they will stand up in the bottommixture preferably witli sufficient strength so that workmen can passover them with rammers.

Up to this stage of the process, the blocks must be kept perfectlyclean, free from dirt, clay, and other objectionable materials, and thejoints are to be kept open down to the point where the bottom mixturepenetrates.

Vith substantially regular blocks such as shown in Fig. 2, the drybottom B does not come up to any great'extent into the joints 34, butwhere more irregular blocks are used,

mixed in a mechanical mixeror grouting machine, and of sufficientfluidity to allow it to run thoroughly into the jointsvand down clean tothe bottom B.

This grout should be applied in suoli manner that the joint' openingsare `completely filled and the excess grout appears onthe Y surface ofthe blocks. It should be broomed or scraped intothe joint openings ifnecessary so as to fill them. It may be necessary to repeat thisgrouting until the joint openings are permanently filled and the groutno longer settles therein. 'I`he surface of the pavement thus groutedshould immediately be broomed to an even smooth surface. i

After the grout has been applied and vany excess removed, the pavementkshould be completely covered with a blanket, which may be of sand,which must be kept moist .for perhaps a week. The pavement shouldV beprotected from all travel for perhaps ten days, during ywhich time themoisture inthe subgrade through capillary attraction works up into thebottom part B of the pavement,

gradually causing it to take itspermanent set.V e l Inl Figs. l and 3, Ishow a foundationin the soil A indicated by 40, 41, 42; The dry bottommixture B is the same, but as the blockseM and O are of dierent depthsand of more irregular shape, thedry bottom mixture B works up into thejoints t4 to a higher point than where the blocks are rectangular.

rIhe construction is the same as Where rectangular blocks are used, andthe joints 44:

' are filledY with a suitable grout L as described above. j

I may form a concrete curb such as E integral with the botto-m B, or Imay use a` In the constructionl shown in Fig. l, if granite blocks M, Oare used, as the granite is stronger than the concrete the fact that itis narrow at the bottom andwider at the top gives a wide or thicksection of concrete and a narrow section of granite which adds tothestrength.

As there is no separate layer or base of a material even slightlydierent from the wearing or load carrying surface, expansion andcontraction by heat Aand cold have no effect on my structure as it is amonolithic and thoroughly bonded slab. It expands and contacts so thatthere is no tendency to crack.

Instead of using a preferably dry mixfor my base B, I may use a dampmix. I find, however, that if a. wet mix of the usual concrete type isused, it is impossible to level the facing blocks because when one isrammed down, another jumps up.

I claim:

1. A monolithic pavement, the bottom of which is formed of aggregate,sand and,

hydraulic cement and water, and the top -of which is formed of stoneblocks having substantially smooth top surfaces and which extend intothe bottom to depths varying substantially whereby the top and bottomare bonded together into a monolithic slab, the spaces between theblocks up to their top faces being filled with a grout of sand,

Y cement and water.

2. A monolithic pavement the bottom of which is formed of aggregate,sand and hydraulic cement and water, and the top of which is formed ofalternately deep and shallow stone blocks which extend into the bottomto various depths whereby the top and bottom are bonded together into amonolithic slab, the spaces between the blocks up to their top facesbeing filled.

3. A monolithic pavement, the bottom of which is formed of aggregate,sand, hydraulic cement and water, and the top Aof which is formed ofstone blocks which extend into the bottom to depths varyingsubstantially whereby the top and bottom are bonded together into amonolithic slab, the spaces between the blocks up to their top facesbeing filled.

4. The process of making monolithic pavements, which consists ofdepositing on a foundation vof compact earth, a thoroughly mixed dryconcrete composed of aggregate, sand and hydraulic cement, thenimbedding therein paving blocks of various depthsso that the dryconcrete will fill the spaces beneath the shallow blocks between thedeep blocks, then ramming or rolling' the blocks to bring their topfaces to an even surface, then sprinkling the mass with suiiicient waterto cause the initial set to the hydraulic cement, then while the mass isstill wet, filling the spaces between the blocks with a grout composedof hydraulic cement, sand and water.

5. The process of making monolithic pavements which consists ofdepositing on a foundation of natural soil a dry concrete composed ofcrushed stone, sand and hydraulic cement thoroughly mixed, thenimbedding therein while the concrete is still dry, paving blocks ofsufficiently irregular depths to thoroughly bond together the dryconcrete and the blocks, then ramming or rolling the blocks to bringtheir top faces to an even surface, then sprinkling the mass withsuflicient water to cause the initial setto the cement, then while themass is still wet, filling the spaces between the blocks with a groutcomposed of hydraulic cement, sand and water and then allowingsufficient time for the concrete to take its substantially permanent setfrom water obtained from the natural soil foundation by capillaryattraction, before tratiic is allowed.

(i. A monolithic pavement, the bottom of which is formed of aggregate,sand and hydraulic cement and water, and the top of which is formed ofstone blocks, certain of said blocks being relatively deep and theothers relatively shallow, said blocks being arranged to form a smoothtop and a relatively shallow block being arranged adjacent a relativelydeep block so that the top and bottom are bonded together into amonolithic slab, the spaces between the blocks up to their top facesbeing filled with a grout of sand, cement and water.

7. rIhe process of making monolithic pavements which consists ofdepositing on the natural soil a bottom part of aggregate, sand andhydraulic cement thoroughly and evenly mixed when dry, and of thenembedding therein stone blocks of which a substantial part are ofdifferent depths from the other part so that the dry mixture will workup between them, and they will stand up, then ramming the blocks tobring their top surfaces to substantially an even level, then moisteningthe top of themix, and then filling the remaining spaces between theblocks to the top thereof.

8. In a pavement, the combination with the natural soil on which itrests, of a monolithic slab of which the bottom part is formed of amixture of aggregate, sand and hydraulic cement mixed when dry to auniform consistency throughout, and the surface is formed of stoneblocks a substantial part of which are of substantially different depthsfrom the other part, such blocks being embedded in the bottom mixturewhen dry so that it extends up between them, and a certain amount ofmoisture, together with a filling which extends substantially up to thetop faces of the blocks.

HERBERT E. FLETCHER.

